Utility of DNA Barcoding in Distinguishing Species of the Family Taeniidae

Abstract

The family Taeniidae comprises many parasitic species, which cause serious zoonoses. However, effective identification of Taeniidae species is a long-standing problem, especially in samples from wild hosts with mixed infections of different Taeniidae species. DNA barcoding analysis of small fragments of the cytochrome c oxidase subunit I (COI) gene has been confirmed as an effective and useful method for identifying Taenia species. We therefore performed DNA barcoding analysis using a 351-bp region of the COI gene to identify 27 taeniid species including 9 in the genus Echinococcus, 2 in Hydatigera, 15 in Taenia, and 1 in Versteria. A total of 484 COI sequences were used to calculate genetic divergence expressed by the Kimura 2-parameter (K2P) distance. The mean intra-specific K2P distance in the family Taeniidae was 0.71 ± 0.17% (±SE), while inter-specific divergences were considerably higher. We found that, generally, a 2.0% optimal barcoding threshold could be set to distinguish taeniid species. Taenia polyacantha and Hydatigera taeniaeformis were the only 2 false-positive species identification cases in this study for their intra-specific divergences above the 2.0% optimal threshold. Their high intra-specific divergences coincided with fact that cryptic divergences exist in these 2 species, to which new taxa were recommended. On the other hand, sister species T. asiatica and T. saginata showed a 2.48 ± 0.83% inter-specific divergence, which was the smallest among all the taeniid species. Although fitting the 2.0% optimal species barcoding threshold, the close genetic relationship between T. asiatica and T. saginata implies that longer mitochondrial DNA sequences like the complete COI sequence are needed to strictly distinguish them. Therefore, we concluded that the barcoding technique based on a 351-bp region of the COI gene is able to distinguish taeniid species except for cryptic T. polyacantha and H. taeniaeformis and should be carefully used in distinguishing the closely related species T. asiatica and T. saginata .

Reappraisal of Hydatigera taeniaeformis (Batsch, 1786) (Cestoda: Taeniidae) sensu lato with description of Hydatigera kamiyai n. sp.

“…Attempts to set optimal barcoding thresholds for delimitation of taeniid species have been made by applying mean K2P distances of the partial cox1 sequence (Galimberti et al, 2012a;Zhang et al, 2014). Slightly different threshold values have been presented (3.6% by Galimberti et al, 2012a;2.0% by Zhang et al, 2014), depending on the calculation method and sequence length.…”

Description and life-cycle of Taenia lynciscapreoli sp. n. (Cestoda, Cyclophyllidea)

“…Although Taenia lynciscapreoli groups with Taenia cf. kotlani , Taenia regis and Taenia hydatigena , the latter of which uses canids as definitive hosts, the genetic distances between these species are at an interspecific level (Zhang et al 2014). The phylogenetic analysis by Lavikainen (2014) included an additional species from felids, i.e.…”

Evaluation of cross-reactivity to Taenia hydatigena and Echinococcus granulosus in the enzyme-linked immunoelectrotransfer blot assay for the diagnosis of porcine cysticercosis

“…We used polymerase chain reaction (PCR) to amplify a 392-bp fragment of the cytochrome c oxidase subunit 1 gene ( cox 1) using primers JB3 and JB4.5 [17, 18]. We then sequenced the PCR products using an ABI 3100 automated sequencer (Applied Biosystems, Foster City, CA), and determined the genetic identity of the species based on alignment of the nucleotide sequences of the cox 1 gene [19].…”